<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
		.code {
		font-family: Arial;
		font-style: italic;
		color: red;
		border: 0;
		padding: 2px 3px;
		letter-spacing: 3px;
		font-weight: bolder;
		}
		.unchanged {
			border: 0;
		}
	</style>
	<script language="javascript" type="text/javascript">  
		var code; //在全局 定义验证码   
		function createCode() {
		    code = "";
		    var codeLength = 6;//验证码的长度   
		    var checkCode = document.getElementById("checkCode");
		    var selectChar = new Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9,'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z');//所有候选组成验证码的字符，当然也可以用中文的   
		  
		    for (var i = 0; i < codeLength; i++) {
		        var charIndex = Math.floor(Math.random() * 36);
		        code += selectChar[charIndex];
		    }
		    //alert(code);
		    if (checkCode) {
		        checkCode.className = "code";
		        checkCode.value = code;
		    }
		}
		  
		function validate() {
		    var inputCode = document.getElementById("input1").value;
		    if (inputCode.length <= 0) {
		        alert("请输入验证码！");
		    } else if (inputCode != code) {
		        alert("验证码输入错误！");
		    createCode();//刷新验证码   
		    } else {
		    alert("^-^ OK");
		    }
		}

	</script>
</head>
<body >
	<form action="#">
    <input type="text" id="input1" /> <input type="text" onclick="createCode()" readonly="readonly" id="checkCode" class="unchanged" style="width: 80px" /><br />
    <input id="Button1" onclick="validate();" type="button" value="确定" />
</form>
</body>
</html>